This invention relates to a fluid-tight holder for a current-limiting fuse.
It is known to protect liquid-cooled electrical apparatus such as a pad-mounted distribution transformer with one or more fuses located inside the apparatus enclosure. Each fuse is located inside a liquid-tight holder and the holder is located inside the enclosure at least partially submerged in the liquid coolant. The holder is, in effect, an open ended container secured at its open end over an opening in a wall of the enclosure so the fuse is accessible for replacement without disturbing the apparatus.
This type of fuseholder is a composite structure of a tubular shell made of insulating materials and three fittings. One fitting is a metal fuse terminal which also closes one end of the tube, the second fitting is a means for mounting the open end of the tube on the wall of the apparatus with the tube opening in register with the wall opening, and the third fitting is a metal fuse terminal located between the other two fittings. One known fuseholder is a filament wound structure. This structure is a shell composed of interlaid filaments bonded together with a resinous material and includng the fittings as integral parts of the structure. Glass fibers bonded together with an epoxy or polyester resin are examples of suitable materials. Resin bonded fibers produce a strong structure which is also a good electrical insulator and impervious to the liquid coolant. However, it has proven difficult to produce a filament wound fuseholder which is leakproof at the interfaces of the fittings with the filament wound body. This is believed to be due chiefly to differences in thermal expansion of the fiber-resin materials and the fitting materials. Because the fuseholder is usually in contact with the liquid coolant, it is usually subjected to the same temperatures as the coolant. These temperatures can range from well below freezing to near boiling of water.
The object of this invention is to provide improved seals at the interfaces of the body and the fittings in a filament wound fuseholder.